Presently different techniques are known to produce a variety of optical fiber cables for telecommunication purposes. Through these optical elements it is possible to establish a physical link among telephone, computer, telecontrol and similar telecommunication centers. Said telecommunication is performed through electronic signals and based on bundles of light rays.
The abovementioned optical fiber filaments are small, with diameters usually smaller than one millimeter. It is convenient to give them adequate protection to use them over long distances. One type of protection which is already in use is what is called an adhered type protection, which is obtained through the extrusion of a plastic or similar material on and in direct contact with said filaments.
The optical cables typically use optical fibers with an adhered fiber protection, as laying elements. In Mexican Patent No. 159491 improvements to said cable are presented, said improvements are characterized because they use loose tubes as laying elements. These loose tubes, in turn, are characterized because they are a protection for one or several optical fiber elements contained within said tubes. Said tubes are also characterized because they contain the filaments, alone or together with a filling material for the protection of the filaments against possible moisture penetration inside the tube.
Dry tubes are tubes which do not contain a filling material and filled tubes are tubes that contain said filling material. In turn, said filling material is characterized because it has a consistency that protects the filaments, is moisture repellent and allows at the same time the movement of said filaments within the tubes.
The improvements to the optical cable are also characterized because the (dry or filled) loose tubes are laid through their unidirectional or bidirectional helicoidal application around a central traction element. This central traction element is characterized because it is used for pulling the optical cable during its installation. Said traction element is also characterized because it has a breaking load capable of withstanding the weight and tension of a continuous (without unions) and finite length of optical cable during the installation. The loose tubes are kept on the central element through the application on said loose tubes of a union element. On this assembly, one or two plastic covers are extruded, under which metal ribbons are to be found, longitudinally placed for the mechanical protection of the optical cable of the present invention.
The applicant has developed an optical fiber cable that improves the previous qualities through a new manufacturing technique.
The improvements to the optical cable are based on a loose tube type construction, said loose tubes are laid in an unidirectional or bidirectional (sz) helicoidal form around a light central element with low mechanical memory. This central element constitutes a traction element when the cable is submitted to tension forces caused by the installation; and an element that balances the expansion and contraction forces caused by the operation of the cable at the limits of the thermal range.
On the core formed by the central element and the loose tubes, an aramide fiber layer or a fiber glass layer is placed which, together with the central element, contributes to reach a higher tension during the installation process. On said assembly one or several plastic covers are applied, said covers support one or two metal ribbons placed longitudinally. As final protection, another plastic cover is applied.